1. Field of the Invention
The present invention relates to the production of polymeric epoxy compositions and more specifically to the production of high-molecular polyepoxides by way of preparing cross-linked polymers with the use of nitrogen-containing compounds.
The invention is of particular advantage where such requirements upon a polymeric composition are imposed as high tackiness to base materials, high impact strength, good heat resistance, good chemical stability, and good elasticity so as to level down irregularities on base materials and to reduce internal strains, as well as long duration time of curing.
Most advantageously the invention can be used for protecting metals from corrosion, particularly for anti-corrosion covering of heat supply lines, oil pipelines, and gas pipelines, wherein the product being conveyed has a temperature of 80.degree. to 120.degree. C.; also, due to high tackiness to iron and concrete and due to good elasticity, the composition of the present invention may be used as a sealing compound for sealing joints and as a glue of high adhesive power.
2. Description of the Prior Art
Epoxy resins are known to be extensively used for preparing corrosion-resistant and wear-resistant sealing compounds and glues which possess high mechanical strength and good chemical stability. Due to high density of their cross-linking, the amine-solidified epoxy resins based primarily on diglycidyl ether of bisphenol A are brittle substances of a glass transition temperature of higher than 20.degree. C.
In practice, however, high hardness and high strength of the amine-solidified epoxy resins are not always necessary. Instead, it is desirable that these resins be of high elasticity and low brittleness. Various methods are taken advantage of to make the resins more elastic and less brittle, but the most of these methods can not be regarded as satisfactory.
Known in the art are epoxy compositions comprising various elastomers with epoxy groups, such as polydienurethane epoxy resin and mixtures thereof with diglycidyl ether of bisphenol A as described in USSR Inventor's Certificates Nos.: 231,796; 316,698; 537,096. Though elastic, these compositions possess low strength and very low tackiness to steel.
It is to be noted that both liquid curing agents (aliphatic diamines and low-molecular polyamides as well as derivatives thereof) and crystalline curing agents (aromatic diamines and derivatives thereof) are used in the above epoxy compositions. From the technological point of view, it is most advisable to employ liquid curing agents, but the properties of polymeric compositions cured therewith are worse than those of the compositions cured with crystalline curing agents.
It is quite clear that the crystalline state of the aromatic diamines makes it difficult to uniformely distribute the components of a composition. Various methods are used to improve the distribution of these components. Among these methods are such as dissolving aromatic diamines in a solvent, melting these aromatic diamines or using them with various liquid modifiers. However, such methods can not always be taken advantage of.
Attemps have been made to liquefy the aromatic diamines without dissolving them in solvents. It is known that in order to cure epoxy compositions, use may be made of liquid eutectic mixtures of the aromatic diamines, such as a mixture of 60-75% m-phenylenediamine and 25-40% methylenediamine. The eutectic mixture is a liquid which can be added to epoxy compositions without any additional operations. However, the properties of the polymeric compositions cured with conventional eutectic mixtures are practically the same as those of the polymeric compositions cured with these curing agents separately. (H. Li, K. Nevill, Spravochnoye rukovodstvo po epoksidnym smolam, Moscow, Energia Publishers, 1973, p. 99).
Known in the art is a composition comprising (polypropylene glycol diurethanediepoxide, diglycidyl ether of bisphenol A, and a curing agent. The curing agent may be polyethylene polyamine and 3,3'-dichlor 4,4'-diaminediphenylmetane (MOCA) (see P. E. Gofman, A. G. Sinayskiy, Novie materiali na osnove epoksidnykh smol, ikh svoystva i oblasti primenenia, part I, Leningrad, LDNTP, 1974, pp. 45-47).
By means of combining (polypropylene glycol) diurethanediepoxide with diglycidyl ether of bisphenol A in various weight ratios and in the presence of the above curing agent it is possible to obtain a wide variety of materials, from hard to highly elastic. However, if (polypropylene glycol)diurethanediepoxide is in excess, the above composition possesses low adhesive power. As the content of diglycidyl ether of bisphenol A is increased, the adhesive power increases as well, but at the same time the composition becomes more brittle. In addition, this composition is characterized by a rather low heat resistance.